1, 4-bis-and 2, 4-bis-di-(triorganosilyl) but-1-enes



3,322,$07 1,4-BlS- AND 2,4-BIS-DI-(TRIORGANQSI1LYL) BUT-l-ENES WilliamK. Johnson, Dayton, Ohio, assignor to Monsanto (Zornpany, a corporationof Delaware No Drawing. Filed July 13, 196i Ser. No. 42,472 5 Claims.(11]. Zed-448.2)

The present invention relates to the dimerizat-ion of w-olefinic silanesand is particularly directed to the process of dimerizing allyl andvinyl hydrocarbon silanes over trialkylaluminum or aluminum hydridecatalysts. The invention is further directed to1,4-bis(trihydrocarbylsilyl) but-l-enes and2,4-bis(trihydrocarbylsilylmethyl)but-1- ones, which are produced in thedimerization process. The invention is further directed totris(trihydrocarbylsilylethyl)aluminum, which is an intermediate as wellas a product in the dimerization of the vinyl hydrocarbon silanes and todi(trihydrocarbylsilylethyl) 1,4-bis (trihydrocarbylsilyl)butyl-aluminumwhich is an additional intermediate.

It has been known heretofore that various olefinic hydrocarbons arecapable of dimerization or other polymerization depended upon theparticular olefinic hydrocarbon and catalyst employed. It has now beenfound that a controlled dimerization of allyl and vinyl hydrocarbonsilanes can be effected with trialkylaluminum or aluminum hydridecatalysts, and that the resulting dimers retain u-olefinic unsaturation.

The catalysts used in the present invention can be represented by theformula:

AlR

in which each R is a straight chain, branched, or cyclic saturatedhy-drocarbyl radical of up to or more carbon atoms, or hydrogen. It ispreferred that at least one R be an alkyl group, and more preferable forall three Rs to be alkyl groups, including cycloalkyl groups,particularly those of up to 10 or so carbon atoms, e.g., methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, hexyl, cyclohexyl, octyl, decyl,etc., although other alkyls can be employed, e.g., dodecyl, eicosyl,etc.; in practice, alkyl aluminums containing no more than 6 carbonatoms in the alkyl group will generally be employed. Other suitablealuminum catalysts are, for example, cyclohexyldiethylaluminum,diethylaluminum hydride, isobutylaluminum dihydride, aluminum hydride,and triphenylethylaluminum.

In general, it will be preferable to employ alkyl aluminum compounds inwhich the alkyl group is branched on the ,B-carbon atom, e.g., suchalkyl groups are isobutyl, Z-methylbutyl, Z-ethylbutyl, etc.; suchbranched alkyl groups are less prone to take part in the dimerizationreaction that the normal alkyl groups, thereby avoiding any substantialco-dimerization reactions and improving the yield and purity of thedesired dimer.

The allyl, vinyl, and other w-olefinic hydrocarbon silanes employed inthe present invention can be represented:

in which n is an integer from zero to 8 or more preferably zero or 1,and each R is a hydrocarbyl radical of up to 10 or more carbon atoms,and ordinarily contains no non-benzenoid unsaturation, and can be thesame as or different from each other R in the molecule; each R can, forexample, be methyl, ethyl, phenyl, o-tolyl, p-tolyl, propyl, isopropyl,butyl, t-butyl, hexyl, cyclohexyl, decyl, etc. It is preferred that R bean alkyl radical of up to 6 carbon atoms, or phenyl.

3,3223%? Patented May 3%), 1967 The dimerization of the allylhydrocarbon silanes can be represented:

CH2 AIR, H 2R SiCHzCH CHz RaSiCHgCIIgCHzCCHzSlR'a in which R and R aredefined as having the meanings set forth hereinabove.

The 2,4-bis(trihydrocarbylsilylmethyl)but-l-ene products of the presentinvention include all such compounds having hydrocarbyl groupscorresponding to those described hereinabove with respect to the allylhydrocarbon silane reactants, particular reference being made to thedefinition of R hereinabove. The products in this group of mostpractical value will probably be 2,4-bis(triphenylsilylrnethyl)but-l-eneand 2,4-bis(trialkylsilylmethyl)butl-enes in which the alkyl group hasfrom 1 to 6 carbon atoms; 2,4-bis(trimethylsilylmethyl)but-Lene, forexample, is conveniently prepared.

The 2,4-bis(trihydrocarbylsilylmethyl)but-l-ene products haveot-olefinic unsaturation and are capable of polymerization by freeradical or Ziegler catalysts, either homopolyrnerization orcopolymerization with vinyl or other monomers, e.g., ethylene, vinylchloride, etc.; the but-l-ene products can also be hydrogenated orotherwise reduced to form the corresponding butanes; the unsaturationalso provides a position for possible incorporation of hydroxyl,carboxyl, or other functional groups. The but-l-ene products may also beuseful as functional fluids for transferring heat or mechanical energy,particularly in high temperature applications, or as additives for mineral oil or other lubricants to improve viscosity. The w-olefinichydrocarbon silanes, in which the olefinic group is further removed fromthe silicon than in the allyl silanes, will dimerize in the same mannerand give products homologous to those obtained with the allyl silanes.

The dimerization of vinyl hydrocarbon silanes occurs in a diflerentmanner than the allyl silanes, and gives products which arenon-analogous to those obtainable by reaction of olefinic hydrocarbonswith trialkylaluminums. The reaction is represented: 3R3SiOH=CHi A111 inwhich R and R have meanings as set forth hereinabove. Whentrialkylaluminums are employed in the above process, the formation ofthe tris (trialkylsilylethyl)aluminum compound in the first step isindicated by liberation of an alkylene, e.g., isobutylene whentriisobutylaluminum is employed, and is confirmed by ethanol quenchingof the reaction mixture of the two components, anethyltrihydrocarbylsilane being the product, for example,ethyltriphenylsilane when vinyltriphenylsilane is the original reactant.

The 1,4-bis(trihydrocarbylsilyl)but-l-enes of the present inventioninclude all such compounds having hydrocarbyl groups corresponding tothose described hereinabove with respect to the vinyl hydrocarbon silanereactants, particular reference being made to the definition of Rhereinabove. The products in this group of most practical value willprobably be 1,4-bis(triphenylsilyl)but-lene and1,4-bis(trialkylsilyl)but-l-enes in which the alkyl 0 group has from 1to 6 carbon atoms; l,4-bis(trimethylsilyl)but-1-ene, for example, isSimilarly,

conveniently prepared. the hydrocarbyl groups in the tris(trihydro H,12.92; Si, 19.58; molecular weight (freezing carbylsilylethyl)aluminumcan be any of the foregoing hydrocaroyl groups as generically orspecifically described, the phenyl, ethyl, and methyl groups being ofparticular interest, and the hydrocarbyl groups of the bis(trihydrocarbylsilylethyl) 1,4-bis(trihydrocarbylsilylbutyl) alumi numintermediates can likewise be any of the foregoing generically orspecifically disclosed hydrocarbyl groups, especially phenyl, methyl andethyl groups. The 1,4-bis (trihydrocarbylsilyl)but-l-enes of the presentinvention have olefinic unsaturation and are capable of polymerizationby free radical or Ziegler catalysis, either homopolymerization orcopolymerization with vinyl or other monomers, e.g., ethylene, vinylcholride, etc.; the unsaturation in the but-l-ene products can also beused to introduce functional groups such as hydroxyl groups, carboxylgroups and the like, or can be hydrogenated or otherwise reduced to formthe corresponding butanes. The but-l-ene products may also be useful asfunctional fluids for transferring heat or mechanical energy, possiblybeing particularly useful in high temperature and low temperatureapplications, or as additives for mineral oil or other lubricants toimprove viscosity, or in general in any applications in which theproperties of a medium molecular Weight, internally unsaturatedsilicon-containing hydrocarbon are desirable.

The catalyst or metal co-reactant employed in the present inventionconsists essentially of trialkylalum-inum or aluminum hydride catalystsand the process is carried out in the absence or substantial absence ofother metals or metal compounds such as metal halides, particularly oftransition metal halides, such as, for example, titanium tetrachloride.The presence of titanium tetrachloride, or other metal compound suitablefor forming a Ziegler ethylene polymerization catalyst with aluminumalkyls or hydrides, causes the allyl silanes to polymerize to solidsrather than to dimerize, and causes the vinyl silanes to give anuncertain mixture of products, depending upon conditions. In the presentprocess, a good yield of dimer is obtained.

The following illustrate certain embodiments of the present invention.In the example, triisobutylaluminum is utilized as an exemplification ofthe alkyl aluminums and aluminum hydrides suitable for use in thepresent invention.

Example 1 A mixture of trimethylvinylsilane (50 g.) andtriisobutylaluminum (2 g.) was heated in a sealed reactor at 200 C. for12 hours. The cooled reaction mixture was diluted with about an equalvolume of anhydrous ether and then shaken out with a 25 ml. portion of H50 followed by 2-20 ml. portions of water. The ether solution was driedover anhydrous magnesium sulfate and the solvent removed bydistillation. The dimer, 1,4-bis (trimethylsilyl)but-1-ene, B.P. 8l83 C.(17 mm.), was obtained 64% yield; 11 1.4354. Analysis calculated for C HSi C, 59.90; H, 12.07; Si, 28.02. Found: C, 59.97; H, 12.08; Si, 27.52.

Example 2 A mixture of triethylvinylsilane (25 g.) andtriisobutylaluminum (1 g.) was heated at reflux. Initially, the pottemperature at reflux was 145 C., but gradually increased so that after60 hours heating, no reflux was noted when the pot was maintained at 200C. The reaction mixture was treated according to the procedure ofExample 1 to isolate 1,4-bis(triethylsilyl)but-l-ene. The dimer, B.P.171-173 C. (15 mm.); n 1.4653, was obtained in 56% yield. Analysiscalculated for C H Si C, 67.57; H, 12.76; Si, 19.76; molecular Weight284.6. Found: C, 67.70; point in benzene), 285.

Examplev 3 A mixture of triphenylvinylsilane (28.6 g., 0.1 mole) andtriisobutylaluminum (1 g., 0.005 mole) was heated at 195 C. As thesilane melted, foaming and gas evolution was noted which would beindicative of an olefin exchange reaction. After heating at 195 C. for24 hours, the reaction mixture solidified at reaction temperature. Thereaction mixture was quenched by a short heating period with 50 ml. ofethanol at reflux and allowed to cool. The crystalline solid wasseparated by filtration and recrystallized from benzene. There wasobtained 18 g. (64% yield) of colorless, crystalline product, M.P. 240C. Analysis calculated for C H Si C, 83.88; H, 6.33; Si, 9.82. Found: C,83.86; H, 6.37; Si, 10.09.

The identity of the l,4-bis(triphenylsilyl)but-l-ene products wasconfirmed by reducing the double bond therein by hydroalumination,followed by cleavage of the carbon-aluminum bond with alcohol to givel,4-bis(triphenylsilyl)butane. Specifically, the tubane product wasobtained by heating at reflux a mixture of1,4-bis(triphenylsilyl)but-1-ene (3.5 g., 6 mmoles) in 50 m1. ofo-xylene with triisobutylaluminum (2 g., 8 mmoles) to cause gasevolution and continuing the heating for a few minutes after gasevolution ceased. The cooled reaction mixture was then treated with 2ml. of isobutano, causing a crystalline solid to separate, which wasthen recrystallized from benzene, to give 2.2 g. 1,4bis(triphenylsilyl)butane, M.P. 2l5216 C. The mixed melting point with asample of 1,4-bis(triphenylsilyl)butane preared by reaction of1,4-dichlor0butane and triphcnylsilyllithium was also 215-216 C. Theinfra red spectra of the two samples were identical. To further confirmthe course of the reaction of the vinyl silanes and trialkylalumiuums asgoing in the indicated manner throughtris(trihydrocarbylsilylethyl)aluminum, followed by reaction withadditional vinyl silane to give di(trihydrocarbylsilylethyl) 1,4(trihydrocarbylsilylbutyl)aluminum as a further intermediate, a reactionmixture of vinyltriphenylsilane and triisobutylaluminum which had beenheated to 140 C. was quenched with ethanol to give ethyltriphenylsilane,thus clearly establishing the presence oftris(triphenylsilylethyl)aluminum, which would then react withadditional vinyl silane to give the product according to the reactionscheme set forth above.

Example 4 A mixture of trimethylallylsilane g.) and triisobutylaluminum(5 g.) was heated in a sealed reactor at 200 C. for 27 hours. Themixture was distilled and 65 g. (68% yield) of dimer, B.P. 96l00 C. (14mm.) was obtained. An analytical sample of the2,4-bis(trimethy1silylmethyl)but-1-ene was redistilled; B.P. 109- C. (22mm.); 1.4439. Analysis calculated for C H Si C, 63.07; H, 12.35;molecular weight, 228.5. Found: C, 63.25; H, 12.25; molecular weight(freezing point in benzene), 228.

Example 5 Allyltriphenylsilane (57 g.) and triisobutylaluminum (2 g.)were heated together at 200 C. Initially, a short period ofeffervescence of liberated isobutylene was noted. After heating for 24hours, the cooled mixture was taken up in the minimum amount of ether.Chilling the ether solution in Dry Ice furnished 27 g. of crude dimer,M.P. 9910l C. Recrystallizations from ethanol furnished 20 g. (36%yield) of dimer, M.P. 108 C. Analysis calculated for C H Si C, 83.93; H,6.71; Si. 9.35. Found: C, 84.03; H, 6.80; Si, 9.11.

The process of the present invention, whether using the allyl, vinyl orother w-olefinic silanes, is generally conducted in the absence of air,oxygen or other reactive gases, and often in an atmosphere of nitrogenor similar gas to insure inert atmosphere, with exclusion of moisture orother materials which would react with the aluminum compound reactants,as will be understood by those skilled in the art. The pressure at whichthe process is conducted is not important, sub-atmospheric, atmospheric,or superatmo pheric Conditions being suitable; often the process isconducted in a sealed container under autogenous pressure to avoid lossof reactant material and to exclude air. The process is carried out atelevated temperatures varying from those relatively low temperaturesjust giving an appreciable dimerization reaction rate up to temperatures at which there is substantial decomposition of the aluminumcompound reactants. Generally, the dimerization is elfected above 100C., particularly at temperatures of about 150 C. to about 225 C. In somecases, the first phase of the reaction to producetris(trihydrocarbylsilylethyl)alurninum in the reaction of the vinylsilanes is readily elTected at temperatures below 150 C. The proportionsof the w-olefinic silane reactants and the aluminum compound reactantscan vary Widely, as it is only necessary to have the aluminum compoundpresent in catalytic amounts, but much larger amounts can be employed.In general, in order to avoid directing the reaction toward preparationof tris(trihydrocarbosilylethyl)aluminum to nearly substantial exclusionof the dimerization, it is desirable to have the aluminum compoundconstitute less than one-third of the silane reactant on a molar basis.Suitable ranges are, for example, 0.01 to 0.2 mole of the aluminumcompound per mole of silane reactant, or often 0.05 to 0.1 mole ofaluminum compound per mole of silane reactant. When the process isconducted in a continuous manner, a small amount of the aluminumcompound can be added at the start and the silane reactant can then beadded continuously or intermittently as consume. The aluminum alkyl canbe recycled provided it has not been contacted With moisture, air, etc.

The reaction mixture can be treated in various manners as illustratedherein as convenient to separate the particular products produced. Oftenthe products will be simply distilled, precipitated or extracted fromthe reaction mixture. In other cases it may be convenient prior toseparation of the dimer product to destroy the concomitant tris-(trihydrocarbylsilylethyl)aluminum compound by hydrolysis, al-coholysisor the like.

While the present disclosure sets forth certain proposals of the courseof the dimerization of allyl and vinyl silanes, 5 and providessubstantiating data to support such proposals, it will be realized thatthe invention covers the dimerization reactions of the allyl and vinylhydrocarbon silanes as claimed, regardless of the mechanism or course ofthe dimerization reaction.

What is claimed is:

1. As a compound, 1,4-bis(triphenylsilyl)but-1-ene. 2. As a compound,1,4-bis(triethylsilyl)but-l-ene. 3. As acompound,1,4-bis(trimethylsilyl)but-l-ene. 4. As a compound,2,4-bis(triphenylsilylmethyl)but-1- ene.

5. As a compound, 2,4-bis(trimethylsilylmethyl)but-1- ene.

References Cited UNITED STATES PATENTS 2,695,327 11/1954 Ziegler et al.260448 2,863,896 7/1956 Johnson 260-448 2,914,520 11/1959 Vandenberg252-429 3,037,005 5/1962 Cooper et al. 260448.2 3,223,686 12/1965 Nattaet a1 260448.2

OTHER REFERENCES Petrov et al.: Chemical Abstracts, 49, 15727i (1955).Polyakova et al.: Chemical Abstracts, 51, 4979d (1957). Topichiev etal.: Chemical Abstracts, 53, 8686b (1959).

TOBIAS E. LEVOW, Primary Examiner. A. LOUIS MONACELL, Examiner.

J. C. LANGSTON, I. R. PELLMAN, J. G. LEVITT,

P. F. SHAVER, Assistant Examiners.

1. AS A COMPOUND, 1,4-BIS(TRIPHENYLSILYL) BUT-1-ENE.